CEE11 10 Example 3.10  Consider a group of 5 potential blood donors – A,B,C,D,E – of whom only A and B have type O+ blood. Five blood samples, one from each individual, will be types in random order until an O+ individual is identified.  Let the r.v. Y=the no. of typings necessary to identify an O+ individual.  The p.m.f of Y is